Floating cylinder and link hoist



April 3 1956 J. M. GWINN, JR 2,740,661

FLOATING CYLINDER AND LINK HOIST /qrraF/VEKS.

April 3, 1956 J. M. GwlNN, JR 2,740,661

FLOATING CYLINDER AND LINK HOIST Filed OCt. 20, 1951 3 Sheets-Sheet 2 April 3, 1956 J. M. GWINN, JR 2,740,661

FLOATING CYLINDER AND LINK HOIST Filed oct. 2o, 1951 s sheets-sheet :s

IN V EN TOR.

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United States Patent() FLOATING CYLINDER AND LINK HIST Joseph M. Gwinn, Jr., Dearborn, Mich., assignor to Gar Wood Industries, Inc., Wayne, Mich., a corporation of Michigan Application October 20, 1951, Serial No. 252,395 9 Claims. (Cl. 298-22) This invention relates to a hydraulic hoisting apparatus of the type that may be employed in dump trucks and, especially concerns direct acting hoists, i. e., hoists wherein the cylinder or piston rod is pivoted directly to the dump body.

With reference to direct acting hoists, it is one object of the invention to increase the moment arm of the lifting force applied to the dump body. The attainment of this object permits lower oil pressures or smaller cylinders to be used. Two means for increasing the moment arm are disclosed herein. The first resides in the support of the cylinder on the chassis by means of a load carrying connection between the cylinder and chassis that is axially spaced from the closed end of the cylinder in the direction of the piston rod which extends out of the other end of the cylinder and which is attached to the dump body. Preferably, this connection is used in combination with a load carrying connection for the closed end of the cylinder which supports the closed end on the chassis for movement in a predetermined path. As a second means to increase the moment arm of the lifting force, the invention takes advantage of the oset rod to body and cylinder to frame pivots which are disclosed and claimed per se in a copending application of the present inventor, Serial No. 164,761, filed May 27, 1950, entitled "Offset Cylinder and Piston Rod Mounting for Hydraulic Dump Bodies, now Patent No. 2,704,221, issued March I5. 1955.

A second object of the invention is to reduce the oil pressure required at low lifting angles. This object is accomplished by increasing the relative axial movement of piston and cylinder at the low angles, this increase being obtained by permitting axial movement of the cylinder in a direction opposite to that of the piston. As a consequence of this increase in the effective length of piston travel, a greater volume of oil must be supplied to the cylinder to lift the body through a given angle. However, the energy required to lift the body through such angle is independent of the hoist and, therefore, since the volume of oil furnished to supply this energy has been increased, the pressure of the oil may be decreased correi.

spondingly.

Other objects and features of the invention will appear upon consideration of the accompanying drawings, in which:

Figure 1 is a plan view of the improved hoist mounted upon a portion of a truck chassis;

Fig. 2 is a side elevation of the structure shown in Fig. l and with the bottom frame of a dump body added, the hoist being shown in lowered position;

Fig. 3 is a section taken on line 3 3 of Fig. 2;

Fig. 4 is a side elevation similar to Fig. 2 but with a side beam of the chassis frame broken away, the hoist being shown in an elevated position;

Figs. 5 and 6 are views similar to Figs. 2 and 4, respectively, but with parts removed to more clearly indicate the operation of the hoist.

In the embodiment of the invention shown in the. drawings, the hoisting mechanism is carried by a conventional subframe 1 which may include longitudinal side beams 3 suitably secured together by transverse brace members 4. The -subframe 1 is supported on top of the truck chassis 5 and is rigidly secured to its longitudinal beams by brackets 7 or the like. While it is preferred in the art to mount the hoisting mechanism on the truck by means ot' a subframe, it is evident that the hoist may be mounted directly on the chassis. The invention is, of course, capable of use without modification in either arrangement and either or both the subframe 1 and the chassis 5 may constitute a frame or mounting for a hoist mechanism embodying the invention.

The hoist apparatus is used to elevate a dump body 9, the bottom only of which is shown in the drawings. The body 9 is illustrated as of the end dumping type, though it obviously could be of another type, and is hinged on a transverse axis to the rear of subframe 1. For this purpose, the subframe has a pair of brackets 11 on its opposite side beams 3 and the body 9 has fixed arms 13 supported on trunnions 15 which are journaled in the brackets 11.

The hoist apparatus includes a hydraulic motor or cylinder 17 which is supported upon and reacts against the subframe 1 and which slidably contains a piston 19 and rod 21 that are connected to and react upon the body 9 at a point above the level of hinge 15. It is therefore evident that when oil is furnished by the pump and valve unit 23 to the forward end of the hydraulic cylinder, i. e., between the closed end 25 of the cylinder and the top of the piston 19, the rod 21 will be forced rearwardly out of the cylinder and will raise the body 9 about its hinge l5. Obviously, so far as the scope of the invention is concerned. reversal of the hoist apparatus 4so that the cylinder is connected to the body and the rod to the chassis or use of the apparatus sideways are equivalent to the arrangement described and claimed herein.

ln accordance with the teachings of the aforementioned copending application, the rod 21 is pivoted to the body 9 on a transverse pivot 23 having its axis offset above the longitudinal axis of the rod. However, it should be noted that this feature of construction, while highly desirable, is not absolutely essential in the practice of the present invention. The offset pivot connection 23 is effected by rigidly mounting the rear end of the rod 21 in a cross head 25 that is journaled in side arms 27 of a mounting plate 29 that is rigidly secured to the bottom of the body 9. This may be referred to as a direct pivot connection between the rod and body to distinguish it from the arm type hoists wherein the rod is connected through links to the body.

In the past, it has been conventional to pivot the forward end of the cylinder 17 to the frame l on a transverse axis which is fixed in position. As a consequence of this type of connection, in combination with a direct pivot connection between the rod and body, the ratio of movement of the body vertically to movement of the piston with respect to the cylinder is a maximum at the beginning of the lifting operation. In other words, one inch of piston travel at the beginning of elevation will raise the body a greater vertical distance than it will in the latter stages of elevation. `he energy requirements are determined by the weight of the body 9 multiplied by the vertical distance through which it is lifted. Within the cylinder 17, the energy applied by the piston 19 through the rod 21 to the body 9 to meet the foregoing requirements equals the force on the piston multiplied by the distance that the piston moves relative to the cylinder. lf the piston movement is small, the force must be high and so therefore must be the oil pressure. This problem is inherent in the hydraulic hoist and has been recognized for a long time. However, all efforts to overcome it appear to have centered on increasing the mechanical advantage of the force applied by the piston to the body in the early stages of lift. The invention makes use of this principle too but it also contemplates an increase in the length of piston travel in the early stages of lift, i. e., decrease in ratio of body lift to piston movement, so that the energy requirements for lifting can be supplied by, in effect, moving a smaller lifting force through a greater distance. With respect to the hydraulic cylinder 17, this means that a greater volume of oil is furnished at a lower pressure to meet the energy requirements during the early stage of lifting.

The foregoing feature of the invention resides in mount ing the cylinder 17 on the frame 1 so that it can move along its axis and thus longitudinally relative to the subframe 1 in addition to the usual pivotal or angular movement about a transverse axis. In other words, there is a longitudinally shiftable, transverse pivot axis on which the cylinder 17 is connected to the frame 1. For this purpose, a transverse mounting plate 31, having aligned trunnions 33 located below the cylinder axis, is rigidly secured to the forward, closed end of the cylinder 17. The trunnions 33 are slidably and pivotally received in horizontal, longitudinal slots 35 that are provided by bearing block assemblies 37 a'xed to the insides of the beams 3. As illustrated, the plate 31 may be used as a convenient mount for the pump and valve unit 23 which furnishes oil to the forward end of the cylinder 17 through a connection 39.

Sliding of the cylinder 17 in the slots 35 is controlled by a pair of tension links 41 that connect the rear end of the cylinder to the subframe 1, the slots 35 being long enough to permit the trunnions 33 to move freely through a stroke governed by the links 41. The links 41 are located on opposite sides of the cylinder 17 and are spaced close to the inside faces of the side beams 3. The rear ends of the links have fittings 43 afiixed thereto and these are pivotally connected to and between pairs of spaced plates 45 by means of aligned transverse pivot pins 47 that are located on a level vertically above the axes of hinge 15 and trunnions 33. The plates 45 may be rigidly secured to a transverse channel 49, forming a part of the subframe 1, which has an inclined face 51 that engages the bottom edges of the links 41 when the body 9 is in its lowered position. The forward ends of the links 41 carry rigid straps or fittings 53 that are pivoted to a plate 55 by means of aligned pins 57 that are suitably journaled in the plate. The plate 55 is bolted or otherwise rigidly affixed to the rear end of the cylinder 17 and preferably, but not necessarily, lies in a plane normal to the axis of the cylinder. lt will be seen that the pins 57 are located on an axis which is spaced below and transverse to the cylinder axis.

A pair of forward links 59 may be used, as shown, to

relieve link load on the cylinder 17. The links 59 extend between and are pivoted on the trunnions 33 at their forward ends and trunnions 37 at their rear ends, being located between fittings 53.

In operation, oil under pressure is supplied by unit 23 to the space between the closed end 25 of the cylinder and the piston 19. This pressure urges the cylinder to move forwardly and the piston to move rearwardly. Elevation is commenced with the hoist in the condition shown in Figs. 2 and 5, hence, as the body 9 elevates and the link 41 pivots upwardly, the cylinder is permitted tokmove forwardly on the bearing surfaces 35 under the inuence of oil pressure on its closed end 25 and under the control of the link 41 and with the beneficial effect on the oil pressure as noted hereinbefore. Forward motion of the cylinder 17 is permitted until the pivot 57 dead centers on a line through the centers of trunnion 33 and pivot 47.

The reaction forces on the cylinder 17 to the force applied by the piston rod act through the trunnions 33 and the hinge 57. The reaction on a trunnon 33 is always normal to surface 35 and since member 41 is a simple link the reaction on hinge 57 has the same direction as the link. The direction of the piston rod force acting on pin 23 can be determined by a force parallelograrn of the reactions (which can be transformed to their intersection at the point 60) and this will show that it' lies on the line 61 when the hoist and body are in the positions shown in Figs. 2 and 5. lt will be readily seen that the line 61 has a substantially greater moment arm about hinge 15 than the line between pin 23 and trunnion 33, the latter line being the direction of the lifting force in a conventional direct acting hoist wherein the only support for the cylinder is a pivotal connection at its forward end. The larger moment arm of the force acting along line 61 permits, of course, a reduction in oil pressure at the early stages of lifting.

As the body 9 is elevated, the hinge 57 approaches dead center and the line of force 61 becomes progressively atter inasmuch as point 60 rises faster than point 23. At the dead center position shown in Fig. 6, the line of lifting force 61 on pin 23 passes through the axis of trunnions 33 (i. e., point 60 is now on the axis of trunnions 33) so that in this position the present hoist presents a force equilibrium similar to the conventional direct acting hoist. lt will be seen that after at least the lowest angles of lift have been passed, the lines 61 of lifting force will intersect the rod axis intermediate the rear end gland or bearing 65 and the pis ton 19 so as to obtain the benefits of non-cocking as pointed out in more detail in the parent case.

Ordinarily, dumping is done at about the angle at which the links dead center, i. e., at about 45 degrees in the hoist illustrated. However, it will be appreciated by those in the art that the principles of this hoist can be used to produce a hoist for elevating a body to substantially higher or lower dumping angles. The links can also be allowed to go over dead center in which case the cylinder will move rearwardly and oil pressure will increase.

It is evident that the principles of the invention, as exemplied herein, may be embodied in other constructions which will fall within the spirit and scope of the invention.

What is claimed is:

l. Hoist apparatus for tilting a body relative to a frame comprising, in combination, a hydraulic cylinder, a piston and rod slidable in the cylinder and adapted to be pivoted directly on the body, means for mounting the cylinder on the frame for angular movement relative to the frame and for longitudinal translation relative to both the frame and piston, and means actuated by angular movement of the cylinder for controlling its longitudinal translation.

2. The invention set forth in claim l wherein said mounting means includes a load transmitting connection between the cylinder and frame spaced from the closed end of the cylinder in a direction toward the end of the rod, said connection permitting angular movement of the cylinder relative to the frame.

3. Hoist apparatus for tilting a body relative to a frame comprising, in combination, a hydraulic cylinder, a frame, means mounting the cylinder on the frame for both longitudinal and angular movement relative to the frame, a piston and rod slidable in the cylinder, pivot means for directly connecting the rod to said body, and a rigid member connecting a portion of the cylinder spaced from said means to the frame and controlling the longi tudinal movement of the cylinder relative to the frame.

4. Hoist apparatus for mounting on a frame having a body mounted thereon for tilting about a transverse axis at the rear of the frame, comprising, in combination, a hydraulic cylinder, a trunnion element transverse to the cylinder and supporting the forward end of the cylinder. said element and thus said cylinder being pivotally and slidably mounted on longitudinal bearing surfaces provided on said frame, a piston slidable in said cylinder and having a rod extending rearwardly out of the rear end of said cylinder, means providing a direct pivotal connection between said rod and the body, a rigid link extending longitudinally of the frame and pivoted at its rear end to thc frame, said link being pivoted at its forward end to the cylinder on an axis transverse to the cylinder and located rearwardly of said trunnion element.

5. The invention set forth in claim 4 wherein the axis of the pivot at the forward end of the link is located below the axis of the cylinder and also located below the axis of the pivot at the rear end of the link when the body is in lowered position whereby the forward end of the link moves forward when the body is raised and forces said cylinder to move forwardly on said bearing surfaces.

6. The invention set forth in claim 5 wherein said bearing surfaces and said link constitute the sole connections of the cylinder to the chassis and wherein said body and the axis about which the body tilts are on opposite sides of the axis of the cylinder.

7. The invention set forth in claim 6 including a link pivoted at its forward end on said trunnion element and at its rear end on the pivot connection between the forward end of the other link and said cylinder.

8. Hoist apparatus for tilting a body relative to a frame comprising, in combination, a hydraulic cylinder having a piston slidable therein and a rod having a direct pivotal connection to the body, and load transmitting means other than said rod connecting axially spaced points on the cylinder to said frame and constituting at least a two point support for the cylinder, said means including a rigid link pivoted to the frame and cylinder and providing for angular movement of the cylinder relative to the frame and longitudinal translation of the cylinder relative to the piston and frame.

9. The invention set forth in claim 4 wherein the pivot at the forward end of said link lies on a straight line between the pivot at the rear end of the link and said trunnion at elevated positions of the body.

References Cited in the le of this patent UNITED STATES PATENTS 2,113,044 Eisenberg Apr. 5, 1938 2,203,059 Dalin June 4, 1940 2,581,662 Hutchinson Jan. 8, 1952 

